The present invention relates to a cohesive bandage, the individual layers or bandage application turns of which adhere only to one another and not to the skin, hair and garments, said bandage being manufactured from a woven material, finely or coarsely knitted fabric or from fleece for immobilizing, supporting, compression or relieving bandages for medical purposes as well as to a method for the manufacture of said bandage.
In the case of cohesive bandages, when bandaging injured parts of the body, solely the overlapping bandage application turns adhere to one another; a sticking together with the skin or hair does not take place. Also, when the bandage is removed, no traces of the adhesive substance adhere to the skin; in contrast to adhesively coated bandages it is possible to remove the bandage painlessly. According to the DE-A-581 676, non-coagulated natural rubber with the addition of anti-aging agents not specified in detail is employed as raw material with cohesive adhesive properties.
According to the DE-A-688 430, a gauze or muslin bandage coated with natural rubber in the dip coating method is known, wherein the proteins present in the natural latex, subsequent to the coating, should be removable by means of a coagulation process involving the use of acetic acid and subsequent washing, whereby an improved shelf life and a non-discoloration of the bandages impregnated in this manner is supposed to be achieved, said advantages being attributed to the absence of the proteins otherwise present in the rubber.
However, the bandages manufactured according to the DE-A-688 430 are subject to the known shortcomings of bandages coated in the dipping process, such as extensive loss of the absorptive capacity and permeability to air as well as of the plasticity and the textile nature. Over and above this, following numerous tests it has become evident that the use of natural rubber without the addition of anti-aging agents holds out no prospects of attaining an adequate storage life.
According to the U.S. Pat. No. 2,238,878, methods for the cohesive structuring of muslin, cheese cloth, butter muslin and similar textiles are known, in conformity with which small fragments of natural rubber are applied to one or both surfaces of the same. In such cases it is intended to maintain the relatively large apertures in the fabric in order to obtain an improved permeability to air. The natural latex dispersion employed in this method is not specified in greater detail as to its composition; in particular no data are furnished regarding the admixture of anti-aging agents and other ancillary agents, so that it has to be assumed that bandages of this type do possess the known drawbacks such as a strong tendency to discoloration, loss of the cohesiveness and becoming smeary due to the effects of aging or of temperature influences.
The U.S. Pat. No. 3,575,782 describes a method for the manufacture of elastic wrapping materials fabricated from fibrous fabrics and highly elastic rubber or polyurethane threads while use is being made of coherent binding agents. A number of pre-stretched rubber threads are supplied to the two non-bound webs of fleece material consisting e.g. of polyester fibers in such a way that these come to lie distortedly between the two layers of fleece material. By the employment of coherent binding agents as, for instance, natural rubber or synthetic polymers, the pre-stretched rubber threads in the laminate are strengthened in such a manner that a cohesive, elastic laminate is produced during the subsequent drying and shrinking process. The rubber-like binding agents of either a natural or synthetic kind give rise to a weakly sticky, adhesive feel, as a result of which a sticking together with skin, hair or garments is hardly given, it is true, however, due to the poor adhesive properties, bandages of this type possess an unpleasant greasy or smeary feel. If this greasy or smeary feel is lost due to e.g. a sterilization operation, then this is also connected with the loss of the cohesiveness. The fleece material laminate bandages manufactured according to this method possess, on account of their construction, a binding agent proportion of at least 50%, so that these bandages do not possess the textile nature desired in the sphere of bandages, but rather exhibit the behavior of a rubber band, which results from the circumstance that the incorporated polyurethane or rubber threads lead to constrictions and varying surface pressure. Moreover, the loss of the permeability to air has to be regarded as a further serious shortcoming.
According to the GB-A-1,297,280, a self-adhesive, non-woven, air-permeable fleece material fabricated from rayon fibers is known. The cohesive coating of the fibrous fleece material is effected by means of a mixture of natural latex and synthetic resin latices, the proportion of synthetic resin latex being by far greater than the proportion of natural rubber. However, in this case, both components serve primarily to strengthen the fleece material. By means of the partial coating with adhesive substance it is intended to achieve an adequate strength coupled with a good permeability to air, the adhesive properties are brought about in dependence of the respective type of mixture used.
The DE-A-491 205 describes a method for the manufacture of cohesive, elastic compression bandages which, due to the partial, striated coating with the adhesive are permeable to both air and water vapor. In the bandages or dressings manufactured according to this method, the strip of fabric is conducted between tangentially disposed coating rollers which are provided with recesses. The desired partial coating is achieved by the recesses in the fluted rollers. As adhesive compound, a mixture of dry rubber latex, potassium oleate, anti-aging agent and silicone oil is used. Prior to the coating operation, the adhesive used has to be disposed as solid matter in a low-boiling solvent, e.g. benzene, which is confirmed further by the low drying temperature of 35.degree. C. which is used.
The DE-A-29 12 129 describes a method for the manufacture of air-permeable, cohesive, highly elastic bandages, the cohesiveness being achieved by a superfine dispersion of latex particles on the fiber surface. The adhesive used is exclusively a stabilized, aqueous rubber dispersion.
As opposed to the bandages coated with adhesive compounds which adhere to almost all articles of daily use and materials and which possess a permanent, aggressive tackiness, and purely cohesive adhesive effect is distinguished in that the adhesive forces are effective solely within the adhesive substance and bring about the internal cohesion of the substance. Consequently, a bandage coated with a cohesive substance only adheres to itself, i.e. layer to layer or bandage application turn to bandage application turn, but not to foreign surfaces such as skin, hair or garments. This cohesive adhesive behavior was up till now chiefly regulated by employing non-vulcanized rubber based on natural latex, whereby appropriate cohesive bandages are produced according to the dipping, lick roll or spraying process while use is made of a, in most cases, 60% latex dispersion (centrifuge latex). In this case it is inevitable to stabilize the latex with ammonia prior to the processing which, due to the negative ionogeity, limits the possibility of mixing with other suitable synthetic polymers or anti-aging agents. Over and above this, it is necessary when employing natural latex, to add antioxidants in the form of special organic compounds, as, for example, sterically inhibited phenols in order to achieve an adequate storage life (aging resistance) and to avoid embrittlement phenomena or desiccation processes. The cohesive adhesive behavior can be varied by mixing with suitable synthetic polymers in such a way that more or less strongly pronounced adhesive properties exist. Chiefly rubber-like latices, as e.g. polyisoprene, polybutadiene, butadiene-styrene, acrylonitrile, butadiene copolymers are used as synthetic polymers.
When employing natural latex as cohesive adhesive, a number of drawbacks will have to be accepted. Despite the addition of antioxidants the storage life is severely limited.
On account of the double bond still present in the rubber molecule, a marked reactivity vis-a-vis atmospheric oxygen exists, as a consequence of which the oxidation processes result in a becoming greasy or smeary or in the embrittlement of the rubber. These effects are accelerated further by the effects of light, heat, radiation as well as of certain chemicals such as heavy metals and the like, so that the natural rubber still has to be regarded as being decidedly sensitive to oxidation. The addition of anti-aging agents entails a number of further drawbacks. Thus various anti-aging agents lead to allergies and dermal irritations in different persons and cannot in each case be looked upon as being completely harmless from a toxicological point of view. Furthermore, some of these antioxidants tend to discoloration, which results in a yellowing or pink coloration of the entire latex substance, the bandage thus becoming unsightly. This effect is partially intensified still further by the packing materials and by the atmosphere. It is known, furthermore, that high temperatures are injurious to the rubber adhesive substance, so that difficulties will arise when appropriate bandages are subjected to heat or steam sterilization. Also the use of other sterilization methods, as, for instance, sterilizations effected with the aid of gamma or beta rays meet with great difficulties since the rubber molecules are partially cracked by the high-energy radiation. The bandages become unsightly and useless (yellowing, greasy/smeary feel, embrittlement, loss of adhesion).
In order to circumvent the known drawbacks of the natural rubber and its mixing with rubber-like synthetic polymers, there has ben no lack of attempts in the past aimed at eliminating these product shortcomings. Thus, by way of example, a search was made for improved antioxidants and better packing materials, without that a sweeping success was achieved.